WO2010097530A1

WO2010097530A1 - Method for managing the automatic stoppage of an automobile

Info

Publication number: WO2010097530A1
Application number: PCT/FR2010/050153
Authority: WO
Inventors: Clément GAMBERONI; Christophe Blond
Original assignee: Renault Sas
Priority date: 2009-02-24
Filing date: 2010-02-01
Publication date: 2010-09-02
Also published as: EP2401495A1; JP5525549B2; JP2012518737A; CN102362063B; KR101651167B1; FR2942505A1; FR2942505B1; EP2401495B1; RU2011139090A; KR20110131230A; RU2522948C2; CN102362063A

Abstract

The invention relates to a method that consists of: a) determining a value representative of the temperature (Tavt) of the exhaust gases flowing in an exhaust duct of said engine upstream from the turbine of a turbocharger; b) comparing said value representative of said temperature with a predetermined threshold value (Tavt_seuil); c) if said representative value is higher than said predetermined threshold value, initiating the timing-out of a first time delay (tempo_in) during which steps a) and b) are repeated and, if during the timing-out of the first time delay, a value representative of said temperature is determined to be lower than said predetermined threshold value, suspending the timing-out of said first time delay and proceeding with step d); d) if said representative value is lower than said predetermined threshold value, initiating the timing-out of a second time delay (Tempo_out) during which steps a) and b) are repeated and, if during the timing-out of said second timing-out, a value representative of said temperature is determined to be higher than the predetermined threshold value, suspending the timing-out of said second time delay, resetting the measure of the timing-out of said second time delay, and proceeding with step c); e) if the first time delay has elapsed and said representative value is higher than said predetermined threshold value, preventing the automatic stoppage of the engine; f) if the second time delay has elapsed and said representative value is lower than said predetermined threshold value, authorising the automatic stoppage of the engine and resetting the measure of the timing-out of the first time delay.

Description

"Management method for the automatic shutdown of the engine of a motor vehicle"

TECHNICAL FIELD TO WHICH THE INVENTION RELATES The present invention relates to a method for managing the automatic stopping of the motor of a motor vehicle and a method of automatically stopping such an engine managed by this management method. BACKGROUND

The so-called "hybrid" engines comprise an internal combustion engine and an electrical part that includes at least one electric starter.

In the supercharged internal combustion engine, fresh air is introduced into an intake duct and compressed by a compressor of a turbocharger, before being conveyed to an intake manifold connected to a combustion chamber of a driving cylinder via an intake valve.

After combustion, the residual exhaust gases are expelled to an exhaust duct through an exhaust valve and drive a driving turbine of said turbocharger placed in this exhaust duct.

The internal combustion engine produces polluting exhaust gases, including carbon monoxide, unburned hydrocarbons, particulates and nitrogen oxide molecules. In "hybrid" engines, it is planned, in order to limit these pollutant emissions, to stop the internal combustion engine when the engine speed is below a predetermined threshold, and then restart it with the electric starter.

Thus, the internal combustion engine stops automatically without driver intervention, for example when the vehicle is stopped at a red light.

Polluting exhaust emissions are thus limited.

However, when the internal combustion engine is thus stopped, the oil flow of this engine is also stopped and the central casing of the turbocharger is no longer cooled by this oil flow. If the automatic engine shutdown is triggered while the temperature of the exhaust gas flowing in the turbine of the turbocharger is very high, these can cause a rise in temperature of the central casing of the turbocharger harmful for the operation thereof.

In particular, the coking of the oil present in this central casing at high temperature produces a solid residue which can block the rotation of the axis of the turbocharger. Exceeding the thermal resistance limits of materials may also affect the operation of this turbocharger.

In order to limit the increase in the temperature of the turbocharger linked to the automatic shutdowns of the internal combustion engine, it is known to use an additional water pump, powered by the electric part of the engine, to cool the turbocharger when the combustion engine internal is stopped. However, the installation of such a pump is expensive and its use induces increased energy consumption.

OBJECT OF THE INVENTION

The object of the present invention is to limit the increase in the temperature of the turbocharger linked to the stoppage of the oil circulation during automatic shutdowns of this engine inexpensively and economically energy.

For this purpose, the present invention proposes a method for managing the automatic stopping of the motor of a motor vehicle, according to which the following steps are performed: a) a value representative of the temperature of the exhaust gases flowing in an exhaust duct of said engine upstream of a turbine of a turbocharger placed in the path of this exhaust duct, b) this value representative of the temperature of the exhaust gas upstream of the turbine is compared with a predetermined threshold value; c) if the value representative of the temperature of the exhaust gas upstream of the turbine is greater than said predetermined threshold value, the flow of a first predetermined time delay Tempo-in is triggered during which it is repeated steps a) and b), if, in step c), during the flow of the first time delay Tempo in, a value representative of said lower temperature is determined at said predetermined threshold value, the flow of this first delay is suspended and step d), d) is carried out if the value representative of the temperature of the exhaust gases upstream of the turbine is lower than said threshold value; predetermined, we triggers the flow of a second predetermined time delay Tempo-out during which steps a) and b) are repeated, if, in step d), during the second time delay Tempo-out, a representative value of said temperature greater than said predetermined threshold value, stopping the flow of the second time delay

Tempo-out, the measurement of this flow of the second time delay is reinitialized and step c), e) is carried out if the first time delay Tempo-in has elapsed and the value representing the temperature of the exhaust gases in upstream of the turbine is greater than said predetermined threshold value, the automatic engine stop is prohibited, f) if the second time delay has elapsed and the value representative of the temperature of the exhaust gas upstream of the turbine is lower than at said predetermined threshold value, the automatic stopping of the motor is allowed and the measurement of the flow of the first time delay is reset.

Thus, thanks to the method according to the invention, the automatic shutdown of the engine is prevented if the temperature upstream of the turbocharger is greater than a threshold value. The circulation of oil for cooling the internal combustion engine can not be stopped and the increase in the internal temperature of the central casing is limited.

According to other advantageous and non-limiting characteristics of the process according to the invention, according to this:

in step c), the first time delay Tempo-in being zero, step e) is carried out directly, prohibiting the automatic stopping of the motor, and in step d), the second time delay Tempo-out being zero, step f) is carried out directly by authorizing the automatic stopping of the motor;

in step c), the flow of said first time delay is measured by the incrementation of a first counter t1 between t1 = 0 and t1 = Tempo-in, in step d), the flow is measured said second time delay by incrementing a second counter t2 between t2 = 0 and t2 = Tempo-out;

steps a) and b) are carried out continuously during operation of the engine;

- In step a), said temperature is measured by a sensor disposed in the exhaust duct, upstream of the turbine of the turbocharger; in step a), the said temperature is estimated from the values of the speed and the load of the engine; in step a) an integration value of the function representative of this temperature as a function of time is determined;

in step b), comparing said value representing the temperature of the exhaust gas upstream of the turbine with a predetermined threshold value as a function of the direction of variation of said representative value;

in step b), said predetermined threshold value is determined as a function of at least one operating parameter of the engine, such as the temperature of the engine oil and the temperature of the engine water.

The invention also relates to a method of automatically stopping the motor of a motor vehicle according to which: g) the speed of this vehicle is determined, h) this determined speed value is compared with a threshold speed value, i) on determines whether the automatic stopping of the motor is authorized or prevented by the implementation of the automatic engine stop management method described above, j) if said determined speed value is lower than said threshold speed value and if automatic stopping of the motor is allowed, the motor is stopped, k) if said determined speed value is lower than said threshold speed value and the automatic stopping of the motor is prevented, the successive steps of this process are repeated from of step g),

I) if said determined speed value is greater than said threshold speed value, the successive steps of this method are repeated from the step

9) - DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT

The description which follows, with reference to the accompanying drawings, given by way of non-limiting example, will make it clear what the invention consists of and how it can be achieved.

In the accompanying drawings: - Figure 1 is a schematic view of the various components of an internal combustion engine allowing the implementation of the method according to the invention;

- Figure 2 is a block diagram schematically showing the various steps of the method of managing the automatic shutdown of the engine according to the invention.

In Figure 1, there is shown an internal combustion engine supercharged having a combustion chamber 23 supplied with fresh air by an intake line 100 and opening downstream on an exhaust line 200.

In the remainder of the description, the terms "upstream" and "downstream" are defined with respect to the direction of flow of the gases in the intake line 100 and the exhaust line 200.

The intake line 100 comprises an intake duct 4 in which fresh air circulates. The fresh air flow rate is measured at the inlet of the intake duct 4 by an air flow meter 1. The internal combustion engine comprises a turbocharger 14 comprising a compressor 2 and a driving turbine 9. The driving turbine 9 is placed in an exhaust duct 16 and drives the compressor 2 placed in the intake duct 4 in order to compress the gas circulating therein.

The driving turbine 9 is connected to the compressor 2 by an axis disposed in the central casing 7 of the turbocharger 14.

The turbocharger 14 is cooled by a circulation of oil not shown in FIG.

Alternatively, the turbocharger 14 can also be cooled by a circulation of water provided by the operation of an additional water pump. The intake duct 4 opens into an intake manifold 6. It comprises an inlet flap 5 located upstream of this distributor 6 whose orientation relative to the axis of the intake duct 4 controls the flow of gas flowing in the intake duct 4 entering the distributor 6.

The distributor 6 is connected to an intake valve 21 of a cylinder 20 of the engine. The gas flowing in the intake duct 4 enters via an intake valve comprising this intake valve 21 into a combustion chamber 23 of the cylinder 20 and an injector 8 is provided which injects the fuel into this combustion chamber 23. .

After combustion, the residual exhaust gases are expelled to the exhaust duct 16 through an exhaust valve having an exhaust valve 22.

The exhaust gases circulate in the exhaust duct 16 to arrive at the driving turbine 9 of the turbocharger 14. They then pass through an exhaust gas treatment system 11 comprising, for example, an oxidation catalyst placed upstream a particulate filter of the exhaust line 200. According to the embodiment shown in Figure 1, a temperature sensor 12 is placed upstream of the turbine 9 of the turbocharger 14. This sensor preferably continuously measures the temperature of the exhaust gas flowing in the exhaust duct 16 at the outlet of the combustion chamber 23, hereinafter called the temperature before turbine and noted Tavt.

This measurement of the temperature before Tavt turbine is transmitted to an electronic control unit 30 of the engine (ECU). This electronic control unit 30 also receives the information recorded by many other sensors of the engine, for example relating to the air flow at the inlet of the intake duct, to the speed and the load of the engine, or to the speed of the vehicle powered by this engine. It controls in particular the positioning of the intake flap 5, the amount of fuel injected by the injector 8 and the moment of this injection. The electronic control unit 30 of the engine further has means for automatically stopping the engine, to stop the internal combustion engine without intervention of the driver, for example by interrupting the injection of fuel into the combustion chamber.

Remarkably, the electronic control unit is programmed to implement the method of managing the automatic shutdown of the engine according to the invention.

For this, the electronic control unit 30 is programmed to perform the following steps, when the internal combustion engine is running: - step a): determining a value representative of the temperature of the exhaust gas flowing in a duct d exhaust of said engine upstream of a turbine of a turbocharger placed on the path of this exhaust duct,

step b): compare this value representative of the temperature of the exhaust gases upstream of the turbine with a predetermined threshold value.

According to the embodiment shown in FIG. 1, in order to carry out step a), the electronic control unit 30 reads the measurement of the temperature before the turbine Tavt measured by the sensor 12.

The predetermined threshold value of the temperature before turbine is noted Tavt_seuil, and is for example between 670 degrees Celsius and 750 degrees Celsius. It is for example determined in step b) as a function of at least one operating parameter of the engine, for example as a function of the engine oil temperature and / or the engine water temperature.

If this temperature before turbine Tavt is greater than said predetermined threshold value in step b), the electronic control unit 30 then performs a step c), by triggering the flow of a first predetermined time delay Tempo-in during which steps a) and b) are repeated.

If, in step c), during the flow of the first time delay Tempo in, the electronic control unit 30 determines a temperature before turbine Tavt lower than said predetermined threshold value, the flow of this first delay is suspended. Tempo-in and step d) is described below.

When the first time delay Tempo-in has elapsed and the value representative of the temperature of the exhaust gas upstream of the turbine is greater than said predetermined threshold value, the electronic control unit performs step e) of the method by prohibiting the automatic shutdown of the engine. The electronic control unit then preferably resumes the execution of the method in step a).

If the temperature before turbine determined in step a) is lower than said predetermined threshold value in step b), the electronic control unit then performs step d) by triggering the flow of a second time delay A predetermined time-out during which steps a) and b) are repeated.

If, in step d), during the second time period

Tempo-out, the electronic control unit determines a temperature before turbine greater than said predetermined threshold value, stopping the flow of the second time delay Tempo-out, resetting the measurement of the flow of this second time delay Tempo-out out and step c) is performed.

When the second time delay has elapsed and the value representative of the temperature of the exhaust gas upstream of the turbine is lower than said predetermined threshold value, the control unit performs step f) of the process by authorizing the automatic motor shutdown and resetting the flow measurement of the first Tempo-in time delay. The electronic control unit then preferably resumes the execution of the method in step a).

The first Tempo-in delay can be zero. The electronic control unit 30 then performs step e) of the method and resumes in step a).

The second delay Tempo-out can also be zero: the unit of electronic control 30 then immediately allows the engine to stop, and resumes in step a).

In practice, an embodiment of this method is shown in FIG. 2. The electronic control unit 30 measures the flow of each of these delays by incrementing a time counter and indicates the state of inhibition of the automatic stopping of the motor by an output variable noted in FIG.

Automatic shutdown which can take two values "authorized" or "forbidden". A first time counter t1 is incremented between the values t1 = 0 and t1 =

Tempo-in to measure the flow of the first delay Tempo-in and a second time counter t2 is incremented between the values t2 = 0 and t2 = Tempo-out to measure the flow of the second delay Tempo-out.

Initially, when the engine is stopped, before introduction of the ignition key by the driver or during an automatic or voluntary stop of the engine, the automatic stop is authorized by default and the first and second counters are initialized to zero. This state of the engine is noted in state 1 in FIG. 2 and is represented in frame 100.

At startup or automatic restart of the engine, it goes into the state noted state 2, shown in frame 200 of Figure 2, in which the engine is running, automatic shutdown is allowed by default and the first and second counters are initialized to zero.

As soon as the engine is started, the electronic control unit 30 preferably continuously performs the above process steps a) and b).

According to this embodiment, in step b), the central unit continuously compares the measured temperature before turbine Tavt with the same threshold value denoted by Tavt_seuil.

According to the embodiment described here, if the temperature before turbine Tavt is greater than the threshold value Tavt_seuil, the electronic control unit 30 triggers the realization of step c) of the method: the motor goes into the state 22 shown in frame 400 of FIG. 2, in which the motor is running, the first counter t1 is regularly incremented, and the second counter t2 is kept at zero.

The authorized or prohibited state of the automatic engine stop is not changed by changing to this state 22 of the engine. In other words, when the electronic control unit shifts the motor from state 2 to state 22, the automatic stop remains authorized in state 22.

If, while the engine is in this state 22, the temperature before turbine Tavt becomes lower than the threshold value Tavt_seuil, the electronic control unit performs step d) of the method by passing the motor in a state 21 shown in the frame 300 of Figure 2, in which the engine is running, the incrementation of the first counter t1 is suspended, and the second counter t2 is incremented. As before, the state of the Automatic Stop variable is not changed.

If, when the engine is in state 2, the measured temperature before turbine Tavt is lower than the threshold value Tavt_seuil, the electronic control unit 30 triggers the realization of step d) of the method by putting the motor in this state 21 shown in frame 300 of FIG. 2. In this case, the first counter t1 which was zero in state 2 of the motor is kept at zero, and the second counter t2 is incremented.

The authorized or prohibited state of the automatic engine stop is not changed by going to this state 21 of the engine. In other words, when the electronic control unit 30 switches the motor from state 2 to state 21, the automatic stop remains authorized in state 21.

If, while the engine is in state 21, the temperature before turbine Tavt becomes greater than the threshold value Tavt_seuil, the electronic control unit 30 performs step c) of the process by putting the engine in the state 22, and the second counter is initialized to zero, while the first counter is incremented. As before, the state of the Automatic Stop variable is not changed.

When the first counter t1 reaches its maximum value Tempo-in, the engine is then in state 22 and the temperature before turbine Tavt is greater than or equal to the threshold value Tavt_seuil. The electronic control unit 30 then moves the motor into the state 3, represented in the frame 500 of FIG. 2, in which the motor is running, the first counter t1 and the second counter t2 are reset to zero and the state of the variable Automatic Stop of the motor indicates that it is prohibited, which carries out step e) of the method. When the second counter t2 reaches its maximum value Tempo-out, the engine is then in state 21 and the temperature before turbine Tavt is less than or equal to the threshold value Tavt_seuil. The electronic control unit 30 then returns the engine to the state 2, shown in the frame 200 of FIG. 2, in which the engine is running, the first counter t1 and the second counter t2 are reset to zero and the state of the variable Automatic Stop of the motor indicates that it is authorized, which carries out step f) of the method. When the engine is in the state 3, the electronic control unit 30 performs steps a) and b) of the method and according to the comparison of the temperature before turbine Tavt measured and the threshold value Tavt_seuil in step b) , the electronic control unit 30 likewise pass the motor in one or other of the states 21 and 22 described above by performing steps c) and d) of the method. Since the state of the Automatic Stop variable is not modified when changing from state 3 to state 21 or 22, automatic shutdown is prohibited in states 21 and 22.

As before, if the second counter t2 is incremented to its maximum value Tempo-out, the electronic control unit 30 puts the motor in the state 2 (step f)), whereas if the first counter t1 is incremented to its maximum value Tempo-in, the electronic control unit returns the motor to state 3 (step e)).

The steps a) and b) of measuring the temperature before the turbine Tavt and comparing this temperature with a threshold value Tavt_seuil are preferably carried out continuously by the electronic control unit 30.

Alternatively, the electronic control unit 30 may be programmed so that steps a) and b) are performed at predetermined times depending on the operation of the motor, or at regular intervals. Alternatively, the electronic control unit estimates, in step a), said temperature before turbine Tavt from the values of the speed and the load of the engine.

According to another variant, the value representative of the temperature before turbine Tavt determined by the electronic control unit is an integration value of the function representative of this temperature as a function of time. For this purpose, the electronic control unit continuously receives the values of the temperature before turbine measured by the sensor 12 and when this measured turbine front temperature exceeds a preliminary threshold value, the electronic control unit determines an integration value of the function representative of this temperature as a function of time, for example by calculating the area situated between the curve representative of the temperature before turbine as a function of time and the line for which the temperature before turbine Tavt is equal to the said preliminary threshold value.

The method for managing the automatic stopping of a motor vehicle engine has a particularly advantageous application for the implementation of an automatic stopping method of this motor comprising according to the invention comprises the following steps: g) determining the speed of said vehicle, h) comparing said determined speed value with a threshold speed value, i) determining whether the automatic stopping of the motor is authorized or prevented by setting the method of managing the automatic engine stop described above, j) if said determined speed value is lower than said threshold speed value and the automatic engine stop is authorized, the engine is stopped, k) if said determined speed value is lower than said threshold speed value and the automatic engine stop is prevented, the successive steps of this method are repeated from step g),

I) if said determined speed value is greater than said threshold speed value, the successive steps of this method are repeated from step g).

In practice, step i) can be performed either following steps g) and h), or permanently during operation of the engine.

If step i) is carried out continuously during the operation of the engine, this is performed before steps j), k) and I) of the automatic engine shutdown process and the electronic control unit 30 is directly responsible the current value of the "Automatic Shutdown" variable to determine whether automatic shutdown is allowed or prohibited.

If step i) is not performed continuously during engine operation, the electronic control unit 30 performs steps a) to e) or f) of the automatic shutdown management method to determine whether the automatic shutdown is allowed or prohibited.

If the value of the vehicle speed determined in step g) is lower than said threshold speed value and the automatic engine stop is authorized, the electronic control unit uses the automatic stop means of the engine.

With the method according to the invention, when the temperature of the exhaust gas flowing in the exhaust duct upstream of the turbine of the turbocharger is greater than the predetermined temperature threshold, the automatic shutdown of the engine is inhibited. Thus, the circulation of oil cooling the turbocharger, the rise in temperature of the central casing of the turbocharger, harmful for the operation thereof, is limited. In particular, the coking of the oil present in this central casing at high temperature is reduced and the thermal resistance limits of the materials are not exceeded.

Moreover, when the temperature before the turbine is lower than the temperature threshold value, automatic engine shutdown is allowed, and the polluting emissions of the engine are thus reduced.

According to other embodiments of the method according to the invention, the engine does not include a temperature sensor placed upstream of the turbine of the turbocharger. The temperature of the exhaust gas is then estimated by calculation or by means of charts from, for example, engine speed and load.

The present invention is not limited to the embodiments described and shown, but the skilled person will be able to make any variant consistent with his mind. Alternatively, it can notably be provided that the electronic control unit 30 compares the temperature before the turbine Tavt with a threshold value which depends on the direction of variation of this temperature before the turbine Tavt. For example, when the temperature before turbine Tavt decreases, the electronic control unit 30 compares the temperature before turbine to a first threshold value Tavt_seuil1, and when the temperature before turbine Tavt increases, the electronic control unit 30 compares the temperature before turbine to a second threshold value Tavt_seuil2. The other steps of the process are unchanged.

It is also possible to raise the threshold value Tavt_seuil of the temperature before turbine when the temperature of the oil of the cooling oil circulation of the turbocharger is below a given threshold.

Claims

1. A method for managing the automatic shutdown of the motor of a motor vehicle, according to which the following steps are carried out: a) a value representative of the temperature (Tavt) of the exhaust gases flowing in a duct exhaust (16) of said engine upstream of a turbine (9) of a turbocharger (14) placed in the path of this exhaust duct (16), b) comparing this value representative of the temperature (Tavt) of exhaust gas upstream of the turbine (9) at a predetermined threshold value

(Tavt_seuil), c) if the value representative of the temperature (Tavt) of the exhaust gas upstream of the turbine (9) is greater than said predetermined threshold value (Tavt_seuil), the flow of a first delay is triggered predetermined time (Tempo-in) during which steps a) and b) are repeated, if, in step c), during the flow of the first time delay (Tempo in), a value representative of said temperature is determined; (Tavt) less than said predetermined threshold value (Tavt_seuil), the flow of this first delay is suspended and step d), d) is carried out if the value representative of the temperature (Tavt) of the upstream exhaust gases of the turbine (9) is lower than said predetermined threshold value (Tavt_seuil), the flow of a second predetermined time delay (Tempo-out) is started during which steps a) and b) are repeated, if, at step d), during the second time delay (Tempo-out) a value representative of said temperature (Tavt) greater than said predetermined threshold value (Tavt_seuil) is determined, the flow of the second time delay (Tempo-out) is stopped, the measurement of this flow of the second time delay is reset (Tempo -out) and step c), e) is carried out if the first time delay (Tempo-in) has elapsed and the value representative of the temperature (Tavt) of the exhaust gas upstream of the turbine (9) is greater than said predetermined threshold value (Tavt_seuil), prohibiting the automatic stopping of the motor, f) if the second time delay (Tempo-out) has elapsed and the value representative of the temperature (Tavt) of the exhaust gas upstream of the turbine (9) is lower than said predetermined threshold value (Tavt_seuil), it authorizes the automatic shutdown of the engine and resets the measurement of the flow the first time delay (Tempo-in).

2. Method according to claim 1, wherein: in step c), the first time delay (Tempo-in) being zero, step e) is carried out directly, prohibiting the automatic stopping of the motor, step d), the second time delay (Tempo-out) being zero, step f) is carried out directly, allowing the motor to stop automatically.

3. Method according to one of the preceding claims, wherein: in step c), the flow of said first time delay (Temp- in) is measured by incrementing a first counter t1 between t1 = 0 and t1 = Tempo-in, in step d), the flow of said second time delay is measured

(Tempo-out) by incrementing a second counter t2 between t2 = 0 and t2 = Tempo-out.

4. Method according to one of the preceding claims, wherein: steps a) and b) are carried out continuously during operation of the engine.

5. Method according to one of the preceding claims, wherein in step a), said exhaust gas temperature (Tavt) is measured upstream of the turbine (9) by means of a sensor (12) disposed in the exhaust duct (16), upstream of the turbine (9) of the turbocharger (14).

6. Method according to one of claims 1 to 4, wherein in step a), said temperature (Tavt) of the exhaust gas upstream of the turbine (9) is estimated from the values of the regime and the engine load.

7. Method according to one of claims 1 to 4, wherein in step a), an integration value of the function representative of this temperature (Tavt) of the exhaust gas upstream of the turbine is determined ( 9) as a function of time.

8. Method according to one of the preceding claims, wherein in step b), comparing said value representative of the temperature (Tavt) of the exhaust gas upstream of the turbine (9) to a predetermined threshold value in function of the direction of variation of said representative value.

9. Method according to one of the preceding claims, wherein, in step b), said predetermined threshold value is determined as a function of at least one operating parameter of the engine.

10. A method of automatically stopping the motor of a motor vehicle according to which: g) the speed of this vehicle is determined, h) comparing this determined speed value with a threshold speed value, i) determining whether the automatic engine stop is authorized or prevented by implementing the automatic engine stop management method according to the one of the preceding claims, j) if said determined speed value is lower than said threshold speed value and the automatic engine stop is enabled, the engine is stopped, k) if said determined speed value is lower than said value threshold speed and that the automatic engine stop is prevented, we take the successive steps of this process from step g),

I) if said determined speed value is greater than said threshold speed value, the successive steps of this method are repeated from step 9)